The Banu Umayya (Arabic: بنو أمية ), also known as the Umayyads (Arabic: الأمويون / بنو أمية Umawiyy; Persian: امویان Omaviyân), were a clan of the Quraysh tribe descended from Umayya ibn Abd Shams. The clan staunchly opposed the Islamic prophet Muhammad, but eventually embraced Islam before the latter's death in 632. A member of the clan, Uthman, went on to become the third Rashidun caliph in 644-656, while other members held various governorships. One of these governors, Mu'awiyah I, became caliph in 661 and established the Umayyad Caliphate. The dynasty ruled and expanded the Caliphate until their overthrow by another Qurayshi clan, the Abbasids, in 750.
Hashim ibn 'Abd Manaf (the paternal great-grandfather of the Islamic prophet Muhammad) and 'Abd Shams ibn Abd Manaf were conjoined twins - born with Hashim's leg attached to Abd Shams' head. It was said that they had struggled in the womb, each seeking to be firstborn. Their birth was remembered for Hashim being born with one of his toes pressed into the younger twin-brother, Abd Shams's, forehead. Legend says that their father, 'Abd Manaf ibn Qusai, separated his conjoined sons with a sword and that some priests believed that the blood that had flown between them signified wars between their progeny (rivalry between the (Hashemite) Abbasid Caliphate and the Umayyad Caliphate would indeed reach a bloody climax in the Abbasid Revolution culminating in 750 CE). The astrologers of Arabia opined that Abd Munaaf had committed a grave error when he separated his sons by means of a sword; they did not regard his deed as a good omen.